This invention relates to microwave radios, and, more particularly, to a radio frequency unit for a microwave radio.
Microwave radio communications are widely used to transfer large amounts of data, such as in earth and space microwave long-distance communications links. They are also of interest for shorter-range, lower-power applications such as the basic voice, video, and data links between a cellular base station and a central telephone office. In such applications, the microwave transmission distance is typically about 1/2-5 miles, the microwave signal is at a specific frequency in the range of about 2-94 GHz, and the power output of the microwave transmitter is about 100 milliwatts. Such microwave communications system are generally termed "point-to-point" systems.
Corresponding to the high-power microwave communications systems, a conventional point-to-point system has three basic physical parts: a signal processing unit (SPU), sometimes termed an "indoor" unit having the baseband radio components, a radio frequency (RF) unit (RFU), sometimes termed an "outdoor" unit having the microwave-frequency radio components, and an antenna. Because a microwave feed is required between the components operating at microwave frequency, the radio frequency unit is located within a few feet of the antenna, which ordinarily is mounted outside and aimed at another point-to-point terminal located some distance away. The antenna is typically a parabolic antenna of the cassegrain type. The signal processing unit may be located quite some distance from the radio frequency unit. An ordinary coaxial cable set extends between the signal processing unit and the radio frequency unit, but a microwave coaxial feed is required between the radio frequency unit and the antenna.
As point-to-point microwave systems become more popular, their physical packaging and aesthetic appearance become more important. The existing radio frequency units and antennas are bulky, heavy, visually obtrusive, and, in many cases, difficult to mount, align, and maintain in alignment. With the proliferation of point-to-point systems in large cities, new mounting space on existing masts and elsewhere has become more difficult to find. Installers must hoist the subsequently installed radio frequency unit and antenna to evermore-precarious locations in order to establish line-of-sight contact with the remote terminal. The radio frequency unit and the antenna must be mounted in close proximity to each other.
To overcome these problems, the assignee of the present invention is developing an integrated point-to-point microwave radio frequency unit and antenna, which is much more compact, lighter in weight, and visually less obtrusive than conventional systems. However, the size and weight of the microwave signal processing components provides a significant barrier to achieving these objectives, and there is accordingly a need for such microwave signal processing components and an architecture which results in smaller size and less weight. The present invention fulfills this need, and further provides related advantages.